I think the volume of the cone is 65.94yd because the radius is 3 and the height is 7 also 3 to the second power equals 9 then 3.14 multiplied by 9 equals 28.26 and finally 28.26 multiplied by 7/3 equals 65.94
The midpoint elevation is the average of the endpoint elevations, their sum divided by 2. When elevation is below sea level, it is represented by a negative number.